Internal refrigerating machine heat exchanger

ABSTRACT

An internal refrigerating machine heat exchanger ( 11 ) which increases the efficiency of the refrigerating machine ( 10 ) comprises a pipe having an internally arranged low-pressure channel and having a substantially larger cross-section than all of the high-pressure channels provided on the outside of the pipe. In addition, the inside width of the low-pressure channel is at least as large as the inside width of the connecting lines ( 17, 21 ). Preferably, the wall of the low-pressure channel is smooth.

The invention relates to a heat exchanger for a refrigerating machine, said heat exchanger being used for pre-heating the coolant supplied by the refrigerating machine compressor. Refrigerating machines, for example, those of air-conditioning systems, such as, for example, those of motor vehicles, are frequently equipped with so-called internal heat exchangers. Regarding this, document DE 100 53 000 A1 discloses a refrigerating machine operating with carbon dioxide as the coolant. In particular, the refrigerating machine is designed for a high operating pressure and for a bursting pressure of 700 bar. The coolant is fed to the compressor via the internal heat exchanger that is configured as a heat exchanger pipe. The coolant, which has been compressed by the refrigerating machine and cooled in the condenser, is then again guided in counter-current direction through the heat exchanger pipe in order to warm up the carbon dioxide flowing to the compressor. Representing a high-pressure channel for the liquefied carbon dioxide, the heat exchanger that is configured as a heat exchanger pipe comprises a central channel which is provided with a ribbed panel for improved heat exchange. A plurality of external channels is provided around the internal channel, said external channels being separated from each other by radially extending intermediate panels. The cross-sectional area of each of the externally located channels is smaller than the cross-sectional area of the central high-pressure channel. The sum of the cross-sectional areas of the external low-pressure channels is greater than the cross-sectional area of the internal high-pressure channel. The heat exchanger pipe is an extruded aluminum sheath.

This heat exchanger pipe is suitable for CO₂ refrigerating machines operating at high pressure. However, this heat exchanger pipe is less or not at all suitable for refrigerating machines designed to operate with other coolants. Specifically, this heat exchanger pipe causes a pressure loss on the suction side of the refrigerating machine, said pressure loss not being of significance when CO₂ is used at appropriately high pressures. At lower operating pressures, however, this loss becomes noticeable and causes the refrigerating machine to experience considerable efficiency losses.

In order to achieve a sufficient heat transfer between the high-pressure channel and the low-pressure channel, the heat exchanger must have a specific pipe length. In order to accommodate this pipe length in a refrigerating machine, it is frequently inevitable—in particular, considering the constrained space conditions found in motor vehicles—to design the heat exchanger as a U-pipe or in another way. This requires that the heat exchanger pipe be designed in a sufficiently bendable manner so that it may be deformed without collapsing its channels.

Considering this, the object of the invention is to provide a refrigerating machine heat exchanger which is characterized by high efficiency, even if the refrigerating machine is not operated with CO₂.

This object is achieved by the internal refrigerating machine heat exchanger in accordance with Claim 1:

The refrigerating machine heat exchanger is provided for heat exchange inside the refrigerating machine in order to cool the coolant fed by the evaporator and for re-heating the cold vapor coming from the evaporator. Due to its suitability for this specific task, it is referred to as an internal refrigerating machine heat exchanger. In accordance with the invention, this heat exchanger consists of a pipe comprising an internal low-pressure channel for connection to the suction side of the coolant compressor and to the high-pressure channels that lead to the evaporator. The low-pressure channel has an essentially cylindrical, not divided, cross-section. Said channel may be exactly cylindrical or even deviate slightly from this form, e.g., it may be polygonal, in particular, have rounded corners. In any event, no diameter variations that would exceed a negligible percentage of 5% to 10% exist along said channel's diameter. Ideally, diameter variations are less than 10%, less than 5%, and preferably much less than 5%.

The high-pressure channels are arranged around the outside of the low-pressure channel and preferably have matching cross-sections. The sum of the cross-sectional areas of the externally located high-pressure channels results in an external cross-sectional area which is significantly smaller than the internal cross-sectional area. Due to these measures, the internal low-pressure channel that is to be connected to the suction side of the refrigerating agent compressor generates almost no appreciable pressure losses. Preferably, the cross-section of the low-pressure channel is at least as large as the cross-section of the feed and discharge pipes, whereby the form of the cross-section of the low-pressure channel preferably matches the form of the cross-section of the adjoining pipes. Preferably, these feed and discharge pipes have a diameter which corresponds to the diameter of conventional serially produced suction lines (minimum of 14 mm). In this manner, acceleration and diffuser losses in the transition between the adjoining pipes and the low-pressure channel are also avoided or minimized.

Preferably, the internal cross-sectional area is at least 60% larger than the external cross-sectional area. In other words, while the internal cross-sectional area can be viewed as given, the external cross-sectional area is minimized. The resultant pressure losses occurring in the high-pressure channel are largely not detrimental to the efficiency of the refrigerating machine. However, in this way, the outside diameter of the heat exchanger pipe is reduced to a minimum. The upper limit can be set at 25 mm and, considering the inventive design, can be maintained at all times. Consequently, the requirements due to the available confined space are satisfied, and it is ensured the heat exchanger pipe can still be bent to sufficiently small bending radii.

Preferably, the wall of the low-pressure channel is smooth and without ribs, in order to minimize the pressure drop over the lower pressure channel when the flow profile is almost rectangular.

Preferably, the pipe consists of extruded light metal, for example, aluminum. In this case, it is made of one piece, without cementing or welding spots. The pipe can be manufactured continuously and cut to the desired length. In this way, it is easily possible to produce different heat exchanger lengths. Alternatively, the heat exchanger pipe may consist of two or more parts. For example, it is possible to configure the low-pressure channel as a pipe that is smooth on the inside and on the outside, and to insert this pipe into an external pipe provided with inward-extending ribs. Alternatively, the low-pressure channel may consists of a pipe that is smooth on the inside and ribbed on the outside, said pipe then being inserted into an external pipe that is smooth on the inside.

Also, the internal pipe, as well as the external pipe, may be provided—on the inside and/or on the outside (i.e., on surfaces facing each other)—with ribs extending in longitudinal direction. The parts (external pipe and internal pipe) of the joined heat exchanger pipe can be cemented together, welded together, pressed together or be otherwise joined, or they may even remain unjoined. These parts may consist of the same or of different materials. While, for example, the internal pipe may consist of aluminum or another metal, the external pipe may also consist of aluminum, of another metal or even of plastic material, optionally with liners, such as, for example, of woven material liners, a reinforced elastomer, a hose arrangement or of another material.

Each high-pressure channel is limited by a radially internal wall section, by two radially oriented wall sections that are at a distance from each other in circumferential direction, and by a radially external wall section that also extends in circumferential direction, whereby the radially internal wall section that extends in circumferential direction is longer than the radical wall sections. In so doing, the externally provided high-pressure channels have a greater width when measured in their circumferential direction than height when measured in their radial direction. This benefits the thermal transfer. On the other hand, the cross-sectional areas of the high-pressure channels remain sufficiently large in order to permit a simple manufacture by means of an extrusion-molding process.

Preferably, the radially internal wall section has a length that is twice that of the radial wall sections, and, preferably, also has a length that is three times that of the radial wall sections. In so doing, the number of externally located high-pressure channels is at most ten, and in the most preferred case, at most six. Then, the heat exchanger pipe can be manufactured efficiently, also displaying relatively low flow resistance inside the high-pressure channels, and can be bent to rather small bending radii, without substantially deforming or even collapsing the external, or even the internal channel.

By maximizing the diameter of the suction channel and thus by minimizing the intake resistance of the compressor, combined with the high rate of thermal transfer of the sufficiently long heat exchanger pipe, the efficiency (COP—Coefficient of Performance) can be improved. Considering the same cooling power, the input driving power, and thus the fuel consumption related thereto, can be lowered.

The heat exchanger may be provided with a coupling device which has a receiving component that can be manufactured as a separate part, for example, an injection-molded part or the like. This part can be joined to one end of the heat exchanger pipe by cementing, for example. The internal channel, which has the shape of a pipe extending away from the heat exchanger, may have a conically widened region that abuts tightly against a conical surface of the receiving component. The widened portion forms a section for the insertion of a coupling plug having an internal channel diameter that preferably matches the channel diameter of the internal channel of the heat exchanger pipe.

The coupling plug may be configured as a separate part or it may be molded to the pipe end. This plug consists essentially of a cylindrical pipe section which has a radial projection at a certain distance from its free end. This projection may consist of a soldered-on ring, of an upset collar, or of any other bead formed on the pipe end.

Due to the simplicity of the form of the receiving component, as well as of the coupling plug, both parts can be manufactured in the simplest manner.

In order to secure the coupling plug in the receiving component in axial direction, a coupling housing having a passage opening is used, whereby the coupling plug can be plugged through said passage opening. The coupling housing is rigidly secured in axial direction on the receiving component. This is achieved by a catch means that connects the coupling housing with the receiving component—preferably in a releasable manner—when the coupling is assembled. The coupling plug itself is connected to the coupling housing by a securing means, for example, by locking engagement. In so doing, the coupling device can be installed in a particularly simple manner. It is only necessary to first bring the coupling housing in engagement with the receiving component, whereupon the coupling plug is inserted through the coupling housing into the receiving opening of the receiving component and secured in the coupling housing. Thus, the desired leak-proof fluid connection is established. In addition, installation requires very little time.

Referring to a preferred embodiment, the catch means is embodied by a minimum of one, and preferably by several, engagement fingers, which extend away from one face side of the coupling housing. These engagement fingers reach behind the shoulder formed on the receiving component and are stopped by the contact face of said shoulder. At the same time, in assembled state of the coupling device, the minimum of one of said engagement fingers contacts the circumferential face of the coupling plug, whereby said coupling plug, together with the shoulder of the receiving component, defines a gap. Measured in radial direction, the ends of the minimum of one of the engagement fingers are thicker than the gap that has formed. As long as the coupling plug is seated in the receiving opening of the receiving component, the coupling housing is thus non-detachably connected to the heat exchanger. Consequently, the coupling plug forms a locking device for the catch means which connects the coupling housing to the receiving component.

The coupling housing preferably consists of plastic material. Preferably, it is a one-piece injection-molded part which can be manufactured in a simple and cost-effective manner. The engagement fingers are preferably joined to the coupling housing so as to form one piece. They exhibit the minimal resilience consistent with the properties of plastic material, and thus can yield inward in order to come into locking engagement with the shoulder of the receiving component.

The securing means for mounting the coupling plug in the coupling housing preferably is a snap ring which is arranged in a snap ring groove provided in the passage opening. The snap ring can interact with a collar provided on the coupling plug or with an outward-extending rib that can abut against the snap ring in axial direction.

To do so, the snap ring has a chamfered insertion face on its outside and has a straight contact shoulder on its inside. As a result of this, the application of external forces makes it impossible to pull the coupling plug out of the coupling housing; however, the snap ring can be expanded, for example, by means of a removal tool, in order to pull the coupling plug out of the coupling housing, and thus be able to open the coupling device.

Preferably, the sealing element that is operative between the receiving component and the coupling plug is arranged in the receiving component. Consequently, the coupling housing has only a holding function. This allows the specification of generous tolerances in the manufacture of the coupling housing.

A particular advantage of the combination of the inventive heat exchanger with the short coupling device presented here is the short overall length of the design in conjunction with the possibility of simple installation and—if necessary, separation or de-installation.

Additional details of advantageous embodiment of the invention are the subject matter of the drawings, the description and the claims. The drawings illustrate exemplary embodiments of the invention. They show in

FIG. 1 an elementary diagram of a refrigerating machine comprising an internal heat exchanger;

FIG. 2 a schematic side elevation of the internal heat exchanger of the refrigerating machine in accordance with FIG. 1;

FIG. 3 a cross-sectional view of the heat exchanger in accordance with FIG. 2, on a different scale;

FIG. 4 an end of the heat exchanger in accordance with FIG. 2 formed by a connector and by a pipe end;

FIG. 5 a modified embodiment of the connector of the heat exchanger in accordance with FIG. 2; and,

FIG. 6 an end of the heat exchanger in accordance with FIG. 2 formed by a connector and a pipe end, in a modified embodiment.

FIG. 1 shows a refrigerating machine 1 as can be used, for example, in the air-conditioning system of a motor vehicle or also in another location. The refrigerating machine 1 includes a compressor 2, which, referring to a motor vehicle, is driven, for example, by the engine of said vehicle or even by a separate electric motor or the like. The compressor 2 comprises an outlet 3 where pressurized coolant is present, and comprises an inlet 4 where said compressor takes in coolant at low pressure. A pressure line 5 leads to a cooling device 6 where the compressed and thus heated coolant is cooled and condensed. Therefore, the cooling device 6 is also referred to as a condenser. The coolant that can be used, for example, is R-134a or another so-called safety coolant, i.e., a coolant that works at low pressure.

At an outlet 7 of the cooling device, the coolant is discharged to another pressure line 8 that leads to a high-pressure inlet 9 of the internal refrigerating machine heat exchanger 11. The latter comprises a high-pressure outlet 12 that is connected to an expansion valve 15 via a pressure line 14. This expansion valve relaxes the coolant that is introduced by an evaporator 16. The coolant evaporates in said evaporator and, as a result of this, absorbs thermal energy from the environment, for example, in order to cool the air in an air-conditioning system or for other purposes. The resultant coolant vapor is then transported from the evaporator, via a low-pressure line 17, to the low-pressure inlet 18 of the refrigerating machine heat exchanger 11. This coolant vapor flows through the refrigerating machine heat exchanger in a direction counter-current to the coolant that is being fed through the high-pressure inlet 9. In so doing, the coolant vapor cools the pressurized coolant, thus heating itself. The coolant vapor is discharged when heated at the low-pressure outlet 19 and transported, via a low-pressure line 21, to the inlet 4 of the compressor 2. The internal refrigerating machine heat exchanger 11 is used to increase the efficiency of the refrigerating machine. This increases the temperature of the coolant flowing to the compressor 2, and thus increases the temperature at the outlet 3 of the compressor. Therefore, the condenser, or cooling device 6, releases a greater amount of thermal energy. Furthermore, the internal refrigerating machine heat exchanger 11 lowers the temperature of the coolant fed to the evaporator 16, thus resulting in a better heat transfer from the evaporator 16 to ambient air.

The refrigerating machine heat exchanger 11 is specifically designed for the requirements of the refrigerating machine 1 if said machine operates with a coolant designed for low pressure such as, for example, R-134a or another so-called safety coolant. FIG. 2 shows the refrigerating machine heat exchanger 11 by itself. For example, it is designed as a U-shaped bent pipe 22 having two legs 23, 24, that are bent away from each other at their upper ends, in which case said legs may be located on a common plane at that point. FIG. 3 shows the cross-section of the pipe 22. Preferably, the pipe 22 has an internal hollow space with a circular cross section, thus forming a low-pressure channel 25. Said pipe's wall does not have indentations, ribs or projections, and is preferably smooth in its circumferential direction, as well as in its longitudinal direction (in FIG. 3, perpendicular to the drawing plane). The low-pressure channel 25 is a single channel—it is not divided; it does not comprise dividing panels or the like.

Several high-pressure channels 27 (27 a, 27 b, 27 c, 27 d, 27 e, 27 f) are arranged around the low-pressure channel 25. The high-pressure channels 27 are separated from the low-pressure channel by a radially internally located wall section 28 which describes an arc of a circle. Viewed in circumferential direction, the high-pressure channels 27 are limited by radially oriented wall sections 29, 30 having a radial length that is substantially shorter than the distance to be measured between them in circumferential direction. Parallel to the wall section 28 is another wall section 31, which describes a circle and which closes the high-pressure channel 27 radially toward the outside.

The low-pressure channel 25 takes up the largest portion of the cross-section of the pipe 22. If the pipe 22 has an outside diameter of 25 mm, for example, the diameter of the low-pressure channel 25 is 15 mm, for example. The height of the high-pressure channels 27 to be measured in radial direction is 3 mm to 4 mm, for example. The angular separation of the wall sections 29, 30 among each other is preferably 60°. Therefore, the distance of the wall sections 29, 30 from each other is also in the range of approximately 18 mm. Therefore, the sum of the cross-sections of all high-pressure channels 27 a through 27 f is clearly less than the cross-sectional area of the low-pressure channel 25. Despite the particularly wide low-pressure channel 25, an extremely small outside diameter is achieved.

This heat exchanger pipe has been optimized in view of the efficiency of the cooling system 1. Pressure losses on the intake side of the compressor 2, which could potentially lead to significant efficiency losses, are avoided. On the other hand, a good heat transfer is reliably ensured and a pipe profile is suggested which can be manufactured in a reliable manner, as well as in the form depicted by FIG. 2.

As is shown by FIG. 2, both ends of the refrigerating machine heat exchanger 22 are provided with connectors 32, 34, where the high-pressure inlet 9, the high-pressure outlet 12, the low-pressure inlet 18 and the low-pressure outlet 19 are located. The design of the connector 33 is shown separately by FIG. 4. This design corresponds to and essentially matches the design of the connector 32.

The connector 33 is cemented, welded or otherwise connected in a fluid-tight manner to the pipe 22. In so doing, part of the internal wall section 28 is exposed, so that said wall section extends farther into the connector 25 than the part formed by the external wall section 31 and the wall sections 28, 29. Two chambers 34, 35 are created in the connector 33 which may be made of an aluminum body, a plastic material body or the like. While the chamber 34 is an annular chamber that communicates with the high-pressure channels 27, the chamber 35 is an approximately cylindrical chamber that communicates with the low-pressure channel 25. Each of the two chambers 34, 35 is provided with connectors, which, in this case, represent the high-pressure outlet 12 and the low-pressure inlet 18. The high-pressure outlet 12 and the low-pressure inlet 18 may be configured as pipe connectors or, as shown, also as hose connectors. It is essential that the cross-section of the chamber 35 substantially match the cross-section of the low-pressure channel 25, which, other than that, also substantially matches the cross-section of the low-pressure inlet 18. In this manner, the fluid flowing through the low-pressure channel 25 is neither accelerated nor slowed down during the transition from the heat exchanger to the adjoining line. In addition, attempts have been made to largely avoid sharp edges and fluid deflections in the low-pressure channel in order to minimize flow resistance.

FIG. 5 depicts an embodiment of a connector 36 that has been optimized in view of this. This connector, like the above-described connector, consists of metal, such as, for example, of aluminum or even of plastic material. This connector can be cemented, soldered or welded to the pipe 22, in which case a type of connection appropriate for the selected material is selected for a lasting fluid-tight connection.

Again, the connector 36 has a chamber 37 for the high-pressure inlet 9 that communicates with the high-pressure channels 27. The high-pressure inlet 9 branches off in radial direction. In contrast, the low-pressure channel 25 ends in a preferably cylindrical chamber 38 having a diameter that largely matches the diameter of the low-pressure channel 25. The chamber 38 changes into the low-pressure outlet 19, which can be configured as a bore with an internal thread, as a fitting seat for the line to be welded or cemented into it, or may be configured otherwise. Preferably, said low-pressure outlet may be dimensioned in such a manner that a pipe or nipple may be inserted or secured in said outlet, whereby its inside width matches the outside width of the low-pressure channel 25, whereby, preferably, a stepless flow transition becomes possible. An identical connector may be provided on the opposite end of the pipe 22. This offers the advantage that the coolant that is under low pressure, flowing toward the compressor and thus displaying only low density, can develop a high flow rate, whereby pressure losses can be largely minimized. This is achieved in that the low-pressure channel 25 has a width which is at least the same as, or greater than, the inside width of the connecting lines, i.e., the low-pressure line 17 and the low-pressure line 21.

FIG. 5 shows the entire heat exchanger 11 with a coupling device 101 that is used for the connection of the low-pressure channel 25 to a fluid-transporting line 103. The line 103, for example, may be a pipe line of an appropriate metal such as aluminum, steel, copper or the like, or it may even be made of plastic material. The end of the low-pressure channel 25 is configured such that it projects as pipe end beyond the heat exchanger 11. This pipe end has a receiving component 104, whereas the pipe end of the line 103 represents a coupling plug 105. A coupling housing 106 is provided to secure the receiving component 104 and the coupling plug 105 attached to each other. For example and preferably, this coupling housing is an injection-molded component of plastic material.

For example, the receiving component 104 is cemented to the end of the low-pressure channel 25. To do so, the end of the low-pressure channel 25 can be appropriately widened after the receiving component 104 has been attached, so that a cylindrical section 107 is formed, said cylindrical section having an inside diameter that is greater than the outside diameter of a cylindrical section 108 of the coupling plug 105.

The expanded section 107 of the pipe end of the low-pressure channel 25 and the receiving component 104 define a receiving opening for the coupling plug 105.

On its orifice, the receiving component 104 has an edge 111 that faces inward. Said receiving component's internal face faces toward the fluid channel 110 and forms a shoulder 112. The shoulder 112 forms an annular contact face that is flat in the present exemplary embodiment. In so doing, said shoulder is arranged concentric and at right angles relative to a central axis 113 of the receiving opening 109. Adjoining the shoulder 112 is an annular cylindrical face 114, which has a diameter that is slightly greater than the outside diameter of the section 108 of the coupling plug 105, but which is, however, significantly smaller than the inside diameter of the other section 107. The latter accommodates a sealing element 115, for example, having the form of an O-ring or the form of another suitable seal.

The coupling housing 106 is held by a minimum of one, and preferably several, engagement fingers 116, 117, 118 at the coupling bushing 104. To do so, these engagement fingers extend in axial direction away from an annular end face of the coupling housing 106 and enclose a passage opening 119 having an inside diameter—at least in the region of the fingers 116, 117, 118—that is only minimally greater than the outside diameter of the section 108. The passage opening 119 is limited by a cylindrical wall in the region of the fingers 116, 117, 118.

The fingers 116, 117, 118 have the same configuration among each other. They are separated from each other by slots 121, 122 provided in axial direction. The fingers 116, 117, 118 consist of the same plastic material as the coupling housing 106, and are an integral component of said coupling housing. They are minimally flexible and can thus yield radially inward. Each finger 116, 117, 118 has, on its free end, a head 123, 124 which is provided with a contact face on the side facing the shoulder 112. This contact face is aligned matching the corresponding contact face of the shoulder 112. On its opposite side, the head 123, 124 is provided with a chamfered face. The radial thickness of the head 123, 124 is greater than the radial width of the gap formed between the face 114 and the shell area of the section 108. Consequently, in conjunction with the shoulder 112, the fingers 116, 117, 118 form an engagement means to secure the coupling housing 106 on the receiving component 104.

Furthermore, on the outside, the coupling housing 106 has essentially a cylindrical form. The passage opening 109 is provided with a snap ring groove 129 having a stepped diameter. A first groove section 131 has a relatively small diameter. An adjoining second groove section 132 has a greater diameter, while a third groove section 133 has a diameter that is between that of the first groove section 131 and the second groove section 132. Furthermore, the passage opening continues to the face side 134 of the coupling housing 106 at a diameter which is slightly greater than that of the section 108.

The snap ring groove 129 accommodates a locking ring 135 that is designed as a snap ring. This snap ring has essentially a circular shape and is notched. On its side facing the face side 134, this ring is provided with a chamfered insertion face. On its opposite side, however, it is essentially plane. In relaxed state, said ring's inside diameter is preferably the same as, or minimally greater than, the outside diameter of the section 108. In relaxed state, the locking ring 135 takes on its smallest diameter. In so doing, it rests against the shoulder formed between the groove sections 131, 132 and cannot enter the groove section 131; however, it can be moved into the groove section 133.

The coupling plug 105 encloses a fluid channel 137 and, for example, forms the end of a pipe line which is provided with an annular bead that is not shown in FIG. 5. However, it may also be designed as a separate part which is later joined to a line, for example, a metal pipe line or a line of plastic material, by soldering, cementing or other suitable joining techniques. On its free end, the coupling plug 105 is provided with a conically tapered end face section 138. This facilitates the insertion of the coupling plug 105 in the receiving component 104. In order to interact with the locking ring 135, the coupling plug 105 is provided, at a certain distance with respect to the external conical face end 138, with an annular rib that is configured as a radial flange. Preferably, the rib 139 is produced by a re-forming process (cold reformation), in the course of which the wall of the section 108 of the coupling plug 105 forms an annular, radially outward extending pleat. This pleat extends beyond the outside diameter of the section 108 and is clearly greater than the inside diameter of the relaxed locking ring 135.

The function of the so far described coupling device 101 is as follows:

The section 108 of the coupling plug 105 is inserted into the passage opening 119 of the coupling housing 106 and through the passage opening 119 into the receiving opening 109 of the receiving component 104, and into the widened end of the low-pressure channel 25 of the heat exchanger 11. In so doing, the section 108 secures the engagement fingers 116 (117), 118 in the gap formed between the outside circumferential face of the section 108 and the inside circumferential face 114. The heads 123, 124 are caught behind the shoulder 112 and thus prevent that the coupling housing 106 can be pulled off the receiving component 104.

Furthermore, the section 108 has compressed the sealing element 115 in radial direction and thus achieved fluid-tightness.

As the coupling plug 105 is inserted farther into the coupling housing 106, the coupling bushing 104 finds the annular rib 139 as an abutment on the chamfered insertion face 136 of the locking ring 135. Consequently, as the coupling plug 105 is inserted farther into the coupling housing 106, the ring 135 is first expanded and then snaps back to its original diameter. Now the rib 139 moves the locking ring 135 into the groove section 133 that is narrower than the groove section 132 where the locking ring 135 could widen beforehand. Consequently, the locking ring 135 secures the coupling plug 105 in the coupling housing 106. Once the latter has itself been secured by the engagement fingers 116, 117, 118 on the coupling bushing 104, the coupling plug 105 can no longer be pulled out of the coupling housing 106 and the coupling bushing 104. In addition, the locking ring 135 centers the coupling plug 105. The fluid-tight connection has thus been established in a safe and lasting manner.

If the coupling device 101 is to be disassembled, a release tool, for example, having the form of a release sleeve or of release pins, is used to push the locking ring 135 back into the groove section 132 in order to be held there. A strong pull on the coupling plug 105 can now cause the locking ring 135 to expand, thus making it possible that the coupling plug 105 can be pulled out of the coupling bushing 104 and the coupling housing.

The receiving component is seated tightly on the external shell surface of the heat exchanger 11. The high-pressure channels 27 open into an annular space 34 which, via a channel 202, is connected to the insertion opening 209. This opening is part of the coupling device 201 which is designed corresponding to the coupling device 101. This opening is used for the connection of a line 203 that communicates with the high-pressure channels 27.

A refrigerating machine heat exchanger 11, which increases the efficiency of a refrigerating machine 1, comprises a pipe 22 having an internal low-pressure channel 25 and a substantially larger diameter than all of the external high-pressure channels 27 located outside the pipe 22. In addition, the inside diameter of the low-pressure channel is at least as great as the inside diameter of the connecting lines 17, 21. The wall of the low-pressure channel 25 is preferably smooth. 

1. Internal refrigerating machine heat exchanger (11), consisting of a pipe (22) that is designed for the connection to the suction side of a coolant compressor (2) and that comprises high-pressure channels (27) which are designed for the connection to the pressure side of the coolant compressor (2), whereby: a. the low-pressure channel (25) has a substantially cylindrical cross-section defining an internal cross-sectional area; b. the high-pressure channels (27) are arranged around the low-pressure channel (25) and are separated from each other by radially arranged intermediate walls (29, 30), in which case the sum of their respective cross-sectional areas defines an external cross-sectional area, and; c. the internal cross-sectional area is larger than the external cross-sectional area.
 2. Heat exchanger in accordance with claim 1, characterized in that the internal cross-sectional area (25) is larger than 1.6 times the external cross-sectional area.
 3. Heat exchanger in accordance with claim 1, characterized in that the low-pressure channel (25) is enclosed by a smooth, non-ribbed wall (26).
 4. Heat exchanger in accordance with claim 1, characterized in that the pipe (22) consists of extruded light metal.
 5. Heat exchanger in accordance with claim 1, characterized in that each high-pressure channel (27) is limited by one radially internal wall section (28), two radially oriented wall sections (29, 30) and one radially external wall section (31), and that the portion of the radially internal wall section (28) adjacent the channel (27) is longer than the radial wall sections (29, 30).
 6. Heat exchanger in accordance with claim 5, characterized in that the portion of the radially internal wall section (28) adjacent the channel (27) is longer than twice the radial wall sections (29, 30).
 7. Heat exchanger in accordance with claim 5, characterized in that the portion of the radially internal wall section (28) adjacent the channel (27) is longer than three times the radial wall sections (29, 30).
 8. Heat exchanger in accordance with claim 1, characterized in that the number of external high-pressure channels (27) is at most
 10. 9. Heat exchanger in accordance with claim 1, characterized in that the number of external high-pressure channels (27) is at most
 8. 10. Heat exchanger in accordance with claim 1, characterized in that the number of external high-pressure channels is at most
 6. 11. Heat exchanger in accordance with claim 1, characterized in that the pipe (22) has a circular outside profile.
 12. Heat exchanger in accordance with claim 11, characterized in that the outside diameter of the pipe (22) is less than or equal to 25 mm.
 13. Heat exchanger in accordance with claim 1, characterized in that the low-pressure channel (25) of the pipe (22) is provided with a connector (37), from which extends the connector (19) of the low-pressure channel in axial direction.
 14. Heat exchanger in accordance with claim 1, characterized in that the low-pressure channel (25) has a width which is at least as large as the width of its connector (19).
 15. Heat exchanger in accordance with claim 1, characterized in that the low-pressure channel (25) has a width which is at least as large as the width of the connected lines (17, 21).
 16. Heat exchanger in accordance with claim 1, comprising: a coupling device (101); a receiving component (104) having a receiving opening (109) changing to a fluid channel (110), said receiving opening being provided with an inward-directed shoulder (112); a coupling plug (105) having a tubular extension (108) which contains a fluid channel (137), whereby said plug can be inserted in the receiving opening (109) and whereby said plug's external circumferential face defines a gap with the shoulder (112); and, a coupling housing (106), which has a passage opening (119) for passage of the coupling plug (105) and is provided with a locking means (135) for axially securing the coupling plug (105) in the receiving component, and which has on its face side facing the coupling bushing (104) at least one catch means (112, 116, 117, 118) that interacts with the coupling bushing (104).
 17. Heat exchanger in accordance with claim 1, comprising: a coupling device (101); a receiving component (104) having a receiving opening (109) changing to a fluid channel (110), said receiving opening being provided with an inward-directed shoulder (112); a coupling plug (105) having a tubular extension (108) which contains a fluid channel (137), whereby said plug can be inserted in the receiving opening (109) and whereby said plug's external circumferential face defines a gap with the shoulder (112), whereby the fluid channel has an inside diameter which matches the inside diameter of the low-pressure channel (25).
 18. Refrigerating machine, comprising: a compressor (20) having an inlet (4) and an outlet (3); a condenser (6) that is connected to the outlet (3) of the compressor (2); an evaporator (16) to which the compressed coolant is fed via an expansion valve (15); and, an internal heat exchanger (11) in accordance with one of the previous claims, said heat exchanger being arranged between the evaporator (16), the compressor (2) and the condenser (6) in order to heat the coolant fed to the compressor (20) and to cool the coolant fed to the evaporator (16). 